Versailles Palace

Versailles Palace was the home of King Louis XIV, the Sun King. Life was lavish in the palace. The cobblestone front courtyard is impressive, with the buildings shining in gold. The golden fence and sculptures are beautiful. Inside, it's interesting to see the Queen's ornate floral bedroom, and the glistening Hall of Mirrors. It only takes half an hour to see the palace. There are endless portraits of royalty on the busy walls.

It can be ridiculously crowded inside the palace, so it's best to see the gardens first thing in the morning, rest in the middle of the day, and then see the palace at 5pm, the last time slot of the day, if you are staying in Versailles town. You must reserve your time slot online when you buy your ticket. The best thing about a visit to Versailles are the Versailles Gardens. They are not crowded, and there is so much to see in them that you could explore them all day long, if your feet could bear it!
When my children were little, we had a children's book by Aliki called The King's Day: Louis XIV of France. It brought the palace of the Sun King to life, and it stayed with us as we recently roamed the palace and grounds. If you can find a similar book for your child, it is a great idea!
Another palace I will never forget is Vaux-le-Vicomte, which also has gardens that make you elated.

Directions

Closed Mondays. Open Tues-Sun 9-6. 
Versailles Palace is a 45 minute metro ride from Paris, on RER C line. There is also a large parking lot outside the main gate, if you drive. You can also stay in Versailles town and see the palace and gardens at a leisurely pace. 
The gardens are open daily from early morning until evening, depending on the time of year.
The ticket situation is confusing. On the day you want to see the palace, hamlet, and gardens, buy the Passport ticket online, for around $32. You will choose a time slot for the palace (this is the only area that requires a time slot), and you can see the Queen's hamlet anytime after noon, and the gardens anytime starting at 8am. To see just the gardens, buy a Musical Gardens or Musical Fountains ticket, for around $11 at one of the gates or online, or go in for free before 9am, during winter (Nov to March), or on Mondays- on free days, the groves are closed. Kids under 18, European kids under 26, disabled people and their cafegiver, enter the palace for free. The park area, by the Grand Canal, is always free to enter. If you leave, you have to enter through a different gate next time. We entered through the Queen's Gate to see the gardens in the morning, and then through the main Honour Gate to see the palace at 5pm, the last time slot (to avoid crowds).

Click on map for interactive view